Researchers found that alcohol consumption was associated with increased dementia risk in a study of more than 500,000 patients, and estimated that reducing the prevalence of alcohol use disorder in the population by half could lower dementia cases by up to 16%.
Heavy drinking and alcohol use disorder showed the strongest associations, and genetic analyses supported a consistent risk increase even at moderate levels of intake. Compared with light drinkers—who were defined as fewer than seven drinks per week and had the lowest dementia risk—nondrinkers, heavy drinkers who consumed more than 40 drinks per week, and patients with alcohol use disorder all had higher dementia rates. Specifically, heavy drinking was associated with a 41% higher risk, and alcohol use disorder was linked with a 51% higher risk. Mendelian randomization analyses, which used genetic variants as proxies for alcohol intake, showed that greater consumption was consistently associated with higher dementia risk. A one standard deviation increase in genetically predicted drinks per week was associated with a 15% higher odds of dementia. Genetically predicted alcohol use disorder was also associated with increased risk.
These findings differed from the observational analyses, which suggested a possible protective effect of light drinking. The authors noted a "U-shaped association between alcohol consumption and dementia (as has been seen in previous studies), seeming to support the proposal that low or moderate alcohol use is associated with lower dementia risk than no alcohol at all."
Led by Anya Topiwala, of the Nuffield Department of Population Health at the University of Oxford in the UK, the researchers examined data from the United States Million Veteran Program and the United Kingdom Biobank. The analysis included 559,559 patients aged 56 to 72 years at baseline. During a mean follow-up of 4 years in the US and 12 years in the UK, 14,540 patients developed dementia and 48,034 died. Alcohol exposure was measured using self-reported weekly intake and a standardized screening tool. Dementia diagnoses were drawn from health records. Models adjusted for demographic, socioeconomic, and health-related factors, including smoking and body mass index. In the US, additional adjustments were made for head injury, post-traumatic stress disorder, and substance use. Longitudinal analyses showed that patients who later developed dementia reported faster declines in alcohol intake over time, raising the possibility that changes in drinking behavior prior to diagnosis may have influenced the observational results.
The study had limitations. Dementia diagnoses based on health records may have been incomplete or misclassified. Genetic analyses were more reliable in patients of European ancestry, but were less precise in other groups, which limited generalizability. Mendelian randomization analyses rely on assumptions that cannot be fully tested, and the estimates reflect lifetime exposure patterns rather than changes in alcohol use during adulthood.
“The pattern of reduced alcohol use before dementia diagnosis observed in our study underscores the complexity of inferring causality from observational data, especially in aging populations,” wrote the authors.
Full disclosures can be found in the published study.
Source: BMJ Evidence-Based Medicine
